The Cost of Unresolved Recovery: Senescence, Inflammation, and Bioenergetic Lock-In

Inflammation is often described as something that should be reduced. But biologically, inflammation is not inherently pathological. It is part of how the body responds to infection, injury, metabolic disturbance, and other forms of stress.

The more important question may be:

Can the inflammatory response finish its job and resolve?

A recent review by Melo-Florián and Melo-Ramírez reframes inflammaging—the chronic, low-grade inflammatory state associated with aging—as much more than persistent elevation of inflammatory cytokines. The authors describe it as a multiscale interface failure, involving immune remodeling, mitochondrial dysfunction, cellular senescence, impaired inflammatory resolution, metabolic dysfunction, microbiome changes, and progressively disturbed communication between tissues.

Their formulation is particularly interesting when viewed alongside our forthcoming perspective on bioenergetic impedance.

From that perspective, chronic inflammation may sometimes be understood not as the primary problem, but as part of what remains when the biological response to repeated challenge cannot complete recovery.

Inflammation is a response that is supposed to end

An acute challenge normally follows a trajectory something like:

Challenge → response → adaptation → resolution → recovery

Immune cells are activated. Energy and substrates are redistributed. Damaged structures are removed. Repair programs begin. Mitochondria, redox systems, protein turnover, vascular regulation, and endocrine signaling all participate.

These processes require energy and resources.

Recovery is therefore not simply what happens when the stressor disappears. It is itself active biological work.

Our bioenergetic-impedance framework focuses on this transition. Bioenergetic impedance refers not simply to low ATP or “mitochondrial dysfunction,” but to a time-dependent constraint on energetic throughput and recovery relative to demand. When demand rises temporarily and the system subsequently restores conductance, buffering, repair, and functional reserve, the challenge can be adaptive. When those processes remain constrained, the system may not return completely to its preceding state.

The trajectory then becomes:

Challenge → response → compensation → incomplete recovery → residual displacement

If another challenge arrives before recovery is complete:

residual displacement + new challenge → greater compensatory requirement → still poorer recovery

Repeated often enough, an initially reversible state may become progressively stabilized.

That is where hysteresis and lock-in become relevant.

Mitochondrial dysfunction may help push the system toward lock-in

There is experimental evidence for such a transition at the cellular level.

Passos and colleagues demonstrated a feedback loop in which persistent DNA-damage signaling activates p21, contributes to mitochondrial dysfunction and reactive oxygen species production, and those mitochondrial ROS then sustain further DNA-damage signaling. After several days, this feedback can lock the cell into what the investigators called “deep” cellular senescence (Passos et al., 2010).

This is important because senescence is not simply the presence of damage. It represents a state transition.

Mitochondrial dysfunction can itself contribute to this transition. Wiley and colleagues experimentally disrupted mitochondrial function and produced a form of mitochondrial dysfunction-associated senescence, accompanied by altered NAD+/NADH balance, AMPK activation, p53 signaling, and stable proliferative arrest (Wiley et al., 2016).

Thus, a plausible sequence is:

persistent energetic/redox constraint→ difficulty restoring mitochondrial and cellular homeostasis→ persistent checkpoint signaling→ stable senescent arrest

This does not mean that every senescent cell arises from bioenergetic impedance. DNA damage, oncogene activation, telomere dysfunction, mechanical injury, and other stressors can independently initiate senescence.

But energetic and mitochondrial constraints may help determine whether an initially adaptive response remains recoverable or becomes stabilized.

Why would evolution preserve senescence?

Because senescence can be protective.

A damaged cell that continues dividing may be far more dangerous to the organism than one that permanently stops proliferating.

Senescence therefore acts as an important tumor-suppressive barrier.

Oncogene-induced senescence removes potentially malignant cells from the proliferative pool. Kuilman and colleagues showed that inflammatory signaling involving IL-6 is not merely an accidental by-product of this process: IL-6 was required for establishment and maintenance of oncogene-induced senescence in their experimental system (Kuilman et al., 2008).

This gives inflammatory signaling one immediate function:

help stabilize the arrest.

The damaged cell has effectively changed its priority.

Instead of:

repair → recover → proliferate

the safer strategy may become:

stop proliferation → maintain arrest → signal the surrounding system.

From the viewpoint of the individual cell, this may look like failure.

From the viewpoint of the organism, it can be protection.

But senescence is not supposed to be the end of the story

A senescent cell does something else that is equally important: it communicates.

Through the senescence-associated secretory phenotype (SASP), senescent cells release cytokines, chemokines, growth factors, proteases, and other signals.

Part of that signaling appears to function as a biological alarm.

In a classic liver model, Kang and colleagues showed that premalignant senescent hepatocytes secreted cytokines and chemokines that helped recruit an immune response. CD4+ T cells together with monocytes/macrophages participated in removing these cells. When this senescence surveillance was impaired, liver cancers developed more frequently in the experimental animals (Kang et al., 2011).

Similarly, restoration of p53 in experimental liver tumors induced senescence and inflammatory cytokine expression, followed by an innate immune response that contributed to tumor clearance (Xue et al., 2007).

So senescence may represent something more sophisticated than cellular shutdown:

The cell stops itself from becoming dangerous, stabilizes that arrest, and broadcasts a request for the organism to remove it.

The full adaptive trajectory may therefore be:

damage→ recovery no longer safe or feasible→ senescent arrest→ SASP / danger signaling→ immune surveillance→ clearance and replacement→ tissue-level resolution

Seen this way, senescence is not necessarily failed adaptation.

It may be the last protective adaptation available when autonomous cellular recovery has failed.

Why spend scarce energy producing inflammatory cytokines?

This creates an apparent paradox.

If the cell is already under energetic or mitochondrial constraint, why maintain an energetically expensive secretory program?

One reason is that bioenergetic constraint is not the same as having no energy.

A senescent cell remains metabolically active. It has stopped investing in proliferation, but it can redirect available energetic and metabolic resources toward survival, maintenance of growth arrest, lysosomal activity, and secretion.

Correia-Melo and colleagues provide an especially revealing example. Removing mitochondria from experimentally senescent cells markedly suppressed many pro-aging and pro-inflammatory features of senescence, yet the cells maintained ATP through enhanced glycolysis. Mitochondria were therefore important not simply for supplying bulk ATP but for generating and sustaining the signaling architecture of the senescent phenotype (Correia-Melo et al., 2016).

That distinction fits the impedance concept well.

The issue is not necessarily:

“Does the cell have ATP?”

It may instead be:

“What functions can its remaining energetic throughput support, and where are those resources being directed?”

Once safe recovery and proliferation are abandoned, available resources may be redirected toward containment and communication.

The energetic expense of cytokine production then makes biological sense. It is not necessarily wasted energy. It may represent investment in an organism-level resolution strategy.

The signal can also protect neighboring tissue

The SASP does more than attract immune cells.

Acosta and colleagues showed that secreted factors from senescent cells can induce paracrine senescence in neighboring cells. Their experiments implicated TGF-β-family ligands, CCL2, CCL20 and inflammasome/IL-1 signaling in this process (Acosta et al., 2013).

In the appropriate context, this may create a temporary protective perimeter around a damaged or oncogenically stressed area:

one dangerous cell arrests → nearby vulnerable cells are restrained → immune surveillance is recruited → damaged tissue is contained.

Other work has shown that cytoplasmic chromatin generated during senescence can activate cGAS–STING, promoting inflammatory signaling that contributes to surveillance of oncogenic stress (Dou et al., 2017).

Again, inflammation can initially be part of the solution.

The problem arises when the solution cannot be completed.

When senescent cells are not cleared

The recent inflammaging review emphasizes precisely this problem.

With aging, immune surveillance, efferocytosis, inflammatory resolution, mitochondrial quality control, and regenerative capacity can all become less effective. Senescent cells may therefore remain in tissues rather than being efficiently removed. Their secretory signals consequently persist instead of terminating.

The sequence changes from:

senescence → signaling → clearance → resolution

to:

senescence → signaling → failed clearance → persistent signaling

Now a mechanism that was initially protective can become a source of chronic burden.

Persistent SASP signaling can recruit and activate immune cells, alter neighboring cells, disturb extracellular matrix, reinforce local senescence, and impose additional metabolic and reparative demands on the tissue.

Inflammation itself can then worsen mitochondrial function and redox balance.

The loop closes:

persistent bioenergetic constraint→ mitochondrial dysfunction→ stable senescent arrest→ persistent SASP because clearance fails→ chronic inflammation and tissue remodeling→ greater energetic and reparative demand→ further bioenergetic constraint

This is what we mean by lock-in.

Not every senescent cell produces the same inflammatory program

There is an important qualification.

Senescence should not be treated as one uniform state.

Wiley and colleagues found that mitochondrial dysfunction-associated senescence produced a modified SASP that lacked much of the canonical IL-1-dependent inflammatory program. Severe alterations in NAD+/NADH and AMPK–p53 signaling changed both the arrest and the secretory phenotype.

This observation is valuable because it suggests that inflammatory output itself may depend on the energetic and metabolic state of the cell.

In other words, there may be limits to how much inflammatory signaling a severely constrained system can sustain.

That makes the relationship among bioenergetics, senescence, and inflammation more nuanced than a simple linear sequence.

From separate hallmarks to an unresolved trajectory

Mitochondrial dysfunction, cellular senescence, and chronic inflammation are conventionally described as interconnected hallmarks or mechanisms of aging.

That description is correct.

But it may not tell us why they become persistent together.

A recovery-dynamics perspective offers another possibility:

transient mitochondrial stress can be adaptive.

Persistent mitochondrial/redox constraint can help stabilize cellular arrest.

Senescence can protect against malignant proliferation and signal for external clearance.

Inflammatory signaling can reinforce arrest, restrain neighboring cells, and recruit immune surveillance.

If clearance succeeds, the episode can still resolve.

If clearance fails, however, the same protective machinery remains active beyond the period in which it is useful.

The hallmarks then begin to reinforce one another.

This is the point at which an adaptive response can become an aging mechanism.

The inflammaging review reaches a closely related conclusion from the immune side: disease emerges when inflammatory signaling loses temporal and spatial precision—when acute responses fail to resolve, repair shifts toward fibrosis, defense toward catabolism, and adaptation toward exhaustion.

Our bioenergetic-impedance perspective asks what may constrain that return.

The answer is unlikely to be energy alone. Structural damage, genomic instability, immune dysfunction, extracellular remodeling, environmental exposures, endocrine regulation, and tissue ecology all matter.

But energetic throughput is one important requirement for repair, clearance, rebuilding, and restoration.

Aging may begin when recovery stops returning us to the same place

This leads to a different way of thinking about inflammaging.

The central problem may not be simply that inflammation increases with age.

It may be that increasingly often:

the biological response cannot finish.

A challenge occurs. Adaptation succeeds enough to preserve immediate function. But recovery remains incomplete.

The next challenge therefore starts from a displaced baseline.

Over time:

slower recovery → incomplete recovery → persistent compensation → hysteresis → lock-in

Mitochondrial dysfunction, senescence, and chronic inflammation may be three visible parts of this trajectory.

From this perspective, the goal should not simply be to suppress inflammation or eliminate every stress response. Those responses may be necessary and protective.

The more fundamental question is:

Why did the system fail to resolve—and what is preventing it from completing recovery?

That may ultimately prove more useful than asking which aging hallmark should be targeted in isolation.

Selected references

Acosta, J. C., et al. (2013). A complex secretory program orchestrated by the inflammasome controls paracrine senescence. Nature Cell Biology, 15, 978–990. https://doi.org/10.1038/ncb2784.

Correia-Melo, C., et al. (2016). Mitochondria are required for pro-ageing features of the senescent phenotype. The EMBO Journal, 35, 724–742. https://doi.org/10.15252/embj.201592862.

Dou, Z., et al. (2017). Cytoplasmic chromatin triggers inflammation in senescence and cancer. Nature, 550, 402–406. https://doi.org/10.1038/nature24050.

Kang, T.-W., et al. (2011). Senescence surveillance of pre-malignant hepatocytes limits liver cancer development. Nature, 479, 547–551. https://doi.org/10.1038/nature10599.

Kuilman, T., et al. (2008). Oncogene-induced senescence relayed by an interleukin-dependent inflammatory network. Cell, 133, 1019–1031. https://doi.org/10.1016/j.cell.2008.03.039.

Melo-Florián, A., & Melo-Ramírez, A. (2026). Inflammaging as a systems-level integrator of disease: Biological foundations of chronic low-grade inflammation. Innovative Medicines & Omics. https://doi.org/10.36922/IMO026230035.

Passos, J. F., et al. (2010). Feedback between p21 and reactive oxygen production is necessary for cell senescence. Molecular Systems Biology, 6, 347. https://doi.org/10.1038/msb.2010.5.

Wiley, C. D., et al. (2016). Mitochondrial dysfunction induces senescence with a distinct secretory phenotype. Cell Metabolism, 23, 303–314. https://doi.org/10.1016/j.cmet.2015.11.011.

Xue, W., et al. (2007). Senescence and tumour clearance is triggered by p53 restoration in murine liver carcinomas. Nature, 445, 656–660. https://doi.org/10.1038/nature05529.